1. Field of the Invention
This invention relates to a solid-state image pickup apparatus for displaying video signals in a predetermined region in a main screen of a television system.
2. Description of the Related Art
A monitoring system is currently known in which a plurality of images are displayed on a single display screen using a plurality of television cameras; video signals obtained by the respective television camera are display as controlled to synchronize with one another. This system is useful when used in monitoring, as a single screen pictures of various sections of a building or various segments of a factory.
This kind of monitoring system having a composite screen is exemplified by a coassigned U.S. patent application Ser. No. 630,282 filed Dec. 19, 1990 for SOLID-STATE IMAGE PICKUP APPARATUS and a coassigned U.S. patent application Ser. No. 720,326 filed Jun. 25, 1991 for IMAGE PICKUP APPARATUS FOR SYNTHESIZING IMAGE SIGNALS AND IMAGE SIGNAL PROCESSING SYSTEM.
To obtain the above-mentioned composite screen, the images of the individual television cameras are inserted in the main screen, and a reproduced image from the main screen and video signals from the individual television camera are supplied to a video signal processor where the image and video signals are synthesized as a single synthesized display signal to be displayed on a television monitor.
In one case, the main screen occupies the entire display screen, and in other case, aninset screen is inserted in the main screen of each monitoring television camera, and in still another case, the display screen is equally divided by the video signals from the television cameras independent of the main screen. Further, the number of subdivided screen parts may be set to be two or more, for example, four or nine. With this composite screen, it is possible to simultaneously monitor the steps of production or the like at various sections of a factory.
The individual subdivided video signal can be given with ease from an ordinary television camera. In practice, however, since the display screen is reduced to an x-th size (x stands for an integer), the individual occupied screen region would become smaller, and as a result, image information must be compressed by omitting or overwriting some of the image elements of a standard television system. Accordingly, with regard to the individual inserted image, an image pickup element whose number of image elements is small may be used; a monitoring television camera using a CCD solid-state image pickup element, for example, can perform an adequate function.
However, in order to enable a plurality of video signals to be displayed on a single display screen either if a main screen and an inset screen are allocated to the entire display screen or if a plurality of inset screens are equally allocated to the entire display screen, display synchronizing signals between the individual video signals should have the same timing. For example, when the horizontal and vertical synchronizing signals of the main screen dominate the display screen or when the video signals are inserted in a predetermined region during the horizontal and vertical scanning time, the horizontal and vertical synchronizing signals of the video signals have to be synchronized with those of the main screen.
In the prior art, controlling of the solid-state image pickup apparatus to synchronize with the main screen was accomplished such as by the construction shown in FIG. 5.
In FIG. 5, for picking up a video signal to be inserted in the main screen, a solid-state image pickup apparatus is used, and more particularly a CCD solid-state image pickup element 1 of the frame transfer system is used. The solid-state image pickup element 1 includes an image pickup portion 1I for photoelectrically converting a monitor image into electrical signals, a storage portion 1S for temporarily storing the image signals, and a horizontal transfer portion 1H for sequentially transferring and outputting the stored image information for one line after another. Therefore, electrical charges produced in the image pickup portion 1I by photoelectric conversion are transferred tot he storage portion 1S for storage, whereupon the electrical charge information of the storage portion 1S is outputted from the horizontal transfer portion 1H as an image Y.
In the CCD solid-state image pickup element 1, in order to insert a small inset screen in a main screen, the number of vertical image elements is set to 1/2 of the main screen, and the number of image elements of the storage portion 1S is also set to the same number.
To drive the CCD solid-state image pickup element 1, the image pickup apparatus is equipped with a CCD driver circuit 2. The CCD driver circuit 2 includes a vertical transfer clock generating circuit 2V for supplying a vertical transfer clock .phi..sub.V to the image pickup portion 1I, a storage transfer clock generating circuit 2S for supplying a storage transfer clock .phi..sub.S to the storage portion 2S, and a horizontal transfer clock generating circuit 2H for supplying a horizontal transfer clock .phi..sub.H to the horizontal transfer portion 1H. To the vertical and horizontal transfer clock generating circuits 2V, 2S, timing signals from a vertical transfer timing control circuit 3V and a horizontal transfer timing control circuit 3H are respectively supplied so that vertical and horizontal reading operations of the CCD solid-state image pickup element 1 are controlled by these timing signals.
The vertical transfer clock generating circuit 2V transfers, according to a vertical transfer timing signal VT, the electric charges, which are photoelectrically converted in the image pickup portion 1I, to the storage portion 1S in the unit of screen and also transfers, according to a horizontal transfer timing signal HT, the electrical charges, which are stored in the storage portion 1S, to the horizontal transfer portion 1H.
Further, the horizontal transfer clock generating circuit 2H, which is controlled by the horizontal transfer timing signal HT for synchronization, outputs the electrical charges, which are transferred from the storage portion 1S to the horizontal transfer portion 1H, for a period which is 1/2 of the horizontal scanning time of the main screen.
With this conventionally CCD driver circuit 2, an inset screen whose size is 1/2 of the main screen in horizontal and vertical directions can be inserted in the main screen. FIG. 6 schematically shows the inset screen inserted in the main screen; the inset screen provided with hatching is inserted in the main screen at an optical position indicated by solid or dotted lines, the area ratio of the inset screen to the main screen being 1/4.
In synthesizing the parent and insect screens, the horizontal and vertical synchronizing signals of the inset screen have to be synchronized with those of the main screen accurately. FIGS. 7A and 7B show this operation timing in the conventional art.
FIG. 7A is a timing diagram of the vertical synchronizing signal, and FIG. 7B is a timing diagram of the horizontal synchronizing signal.
VD and HD designate vertical and horizontal synchronizing signals, respectively, of a main screen. As shown in FIG. 5, the vertical and horizontal transfer timing control circuits 3V, 3H operate according to the vertical and horizontal synchronizing signals Vd, Hd, respectively, of the main screen. As shown in FIG. 6, since an inset screen is to be inserted during the vertical and horizontal scanning time of the main screen, vertical and horizontal reading from the CCD image pickup element 1 to form the inset screen have to be started respectively at the timing delayed by a predetermined time from the main screen.
As shown in FIGS. 7A and 7B, vertical and horizontal transfer timing signals VT, HT are outputted at the timing delayed by a predetermined time from the start-up of the vertical and horizontal synchronizing signals VD, HD. In each of the vertical and horizontal transfer timing control circuits 3V, 3H, the respective output timing of the vertical and horizontal transfer timing signals VT, HT is set with the delay of 0 to V/2 (V stands for a vertical scanning time of the main screen) or 0 to H/2 (H stands for a horizontal scanning time) from the respective synchronizing signals VD, HD of the main screen. Therefore, the position from which displaying of the inset screen in the main screen is to be started can be determined by this delay time.
As indicated by solid lines in FIGS. 7A and 7B, the vertical transfer timing signal VT is set to be displayed by V/3 time from the vertical synchronizing signal VD of the main screen, and the horizontal transfer timing signal HT is set to be delayed by H/2 time from the horizontal synchronizing signal HD of the main screen. At that time, the inset screen to be inserted in the main screen will be displayed, as an image whose area is 1/4 of the parent, at a position that is shifted by 1/2 downwardly (in the vertical direction) and by 1/3 rightwardly (in the horizontal direction).
As indicated by dotted lines in FIGS. 7A and 7B, when the vertical transfer timing signal VT and the horizontal transfer timing signal HT are set to be delayed by V/2 and H/3, respectively, each transfer timing of the CCD image pickup element 1 is changed so that, as indicated by dotted lines in FIG. 6, the image I of the inset screen will be inserted at a position that is displaced downwardly (in the vertical direction) by 1/2 and rightwardly (in the horizontal direction) by 1/3.
Therefore, by setting a delay time of the vertical transfer timing signal VE to an optional value, the vertical position of the inset screen to be inserted in the main screen is determined. Likewise, by setting a delay time of the horizontal transfer timing signal HT to an optional value, the horizontal position of the inset screen to be inserted in the main screen is determined.
The size of the inset screen shown in FIGS. 5, 6 and 7 has a 1/2 length either in the vertical direction or in the horizontal direction, compared to the main screen. As a result, it is preferable to set the vertical and horizontal transfer timing signals VT, HT to be delayed by at most V/2 and H2 from the vertical and horizontal synchronizing signals VD, HD, respectively, of the main screen so that the inset screen will not separated vertically or horizontally in the main screen.
Therefore, a video signal Y of the inset screen has a vertical and a horizontal video time which is 1/2 of the respective scanning time v, 1H of the main screen as shown in FIGS. 7A and 7B, and so this video signal Y is displayed as an image having an area reduced by 1/2 of the main screen either vertically or horizontally. Of course, for outside the display region, vertical and horizontal blanking signals VBL, HBL are added to the video signal Y, which is from the CCD image pickup element 1, except the video time region of the inset screen, so that any noise is prevented without fail from being mixed in the video signal of the main screen.
Though there is no detailed illustration, the video signal Y of this inset screen is synthesized with the video signal of the main screen by a video signal processor, and the resulting composite signal is supplied to a television monitor.
Thus, when reading the video signal of the inset screen from the CCD solid-state image pickup apparatus, each of vertical and horizontal transfer timing signals from the CCD image pickup element 1 is determined to be delayed by a predetermined time from the blanking signal of the respective synchronization signal VD, HD of the main screen. At that time, the CCD driver circuit not only should control these transfer timing signals VT, HT but also should process the video signal Y of the inset screen in conformity with the television formatting system of the screen. Various kinds formatting signals needed for this signal processing are horizontal and vertical synchronizing signals, for example, included in the video signal Y of the inset screen. Each of these vertical and horizontal synchronizing signals also should be set to be delayed by a predetermined time from the blanking signal of the respective synchronizing signal VD, HD of the main screen, thus synchronizing the synchronizing signals of the main screen correctly.
Consequently, each time when the display position of the inset screen in the main screen is changed, the operation mode of the synchronizing signal generating circuit should be changed in synchronism with the main screen, thereby making the CCD driver circuit complex. More particularly, in a monitor camera, which should be small-sized using a CCD solid-state image pickup apparatus and in which scanning should be simplified, the CCD driver circuit would be complex, thus requiring much more wiring for each circuit. As a result, the monitor camera would be large-sized.